It turned out that the milling robot arm of the milling robot according to DE 198 15 579 C1 can start to vibrate, both in the axial and in the radial directions, when there are very high engagement forces on the milling head due to the unavoidable inherent elasticity of the cables, which can make precise work difficult or even impossible. In addition, the design requires an independent control unit for each cable, which drives up the manufacturing costs and the control difficulty. The swiveling motion is also not expansive, which is why the use of different sizes of milling robots is required for different pipeline sizes, because only one joint member is available for each swivel direction. The compressed-air supply line for the milling head is outside of the milling robot arm and is consequently exposed to dirt and mechanical interference.
An inspection robot for pipe systems is known from DE 199 56 421 C2 with a camera head that is arranged on an elastic hose with a closed volume fastened down in a spiral; a leaf spring that is fastened down on both ends and that is matched with regard to its rigidity is attached on one side of the hose between the hose and the spiral. The leaf spring makes it possible to bend the tip with the camera head in a pneumatically adjustable way in proportion to the pressure when the hose is pressurized.
A device for inspecting sewers with a bending module that can be controlled in curves at the free end of a feed-unit housing is known from DE 20 2004 002 132 U1. The bending module essentially consists of a cylindrical bending jacket sealed against the atmosphere and a securing insert arranged on at least one side that prevents the axial expansion of the bending jacket during pressurization.
A bend decontamination packer for pipeline and sewer decontamination with an interior core in the form of a hose, a band, a cable or a chain that limits the longitudinal extension of the stretchable exterior cover is described in DE 10 2008 021 956 A1.
None of these devices or similar devices are torsionally rigid, either with regard to the rubber jacket or with regard to the core, which is why they are unsuitable for supporting rotating milling tools.